1. Field of the Invention
This invention relates to the dyeing of soap and synthetic detergent bars. In another aspect, this invention relates to the problem of increasing efficiency in the production of differently colored soap and detergent bar lots. In particular, the invention relates to the problem of introducing high concentrations of dyestuff to soap and detergents at the amalgamator in the presence of a slurry heavily laden with optional ingredients.
2. Description of the Prior Art
Generally the method of making bar soap products is as follows: Fatty acids are blended with caustic soda in saponification towers or boiled in soap kettles (in the older processes). The resulting flowable product, called neat soap, is pumped to a dryer where it is dried and scraped off in chip form. Thereafter the soap chips or pellets are sent to an amalgamator for blending with whatever soap additive a particular soap maker may want to include, such as for example, dyes, emollients and perfumes. The additives are carried in a slurry which has been mixed in a separate tank. The slurry vehicle (usually water) provides the additional moisture needed to blend the dry chips of neat soap and the additives to a homogeneous mixture. From the amalgamator the blended product is sent to a plodder in which it is further blended, compressed and ultimately extruded as a continuous ribbon of soap. The ribbon is cut into slugs which are then stamped and wrapped for market.
Traditionally, soap and synthetic detergent bars are white or pastel colored. In the art of making pastel bars, the dye is usually added in low concentrations at the amalgamator stage where the dispersion in the soap is accomplished by wetting the dye with the liquid soap and water.
Intensely-colored bars incorporating relatively high concentrations of dye have become popular in recent years and are now a small but valuable part of the market.
The problem if dyeing such bars was first approached traditionally, using the method previously known for dyeing pastel bars in the amalgamator; that is, wetting the dye with liquid soap and water. However, the bars thus made were speckled and streaked due to poorly dispersed and/or undissolved dyestuff. The problem was intensified by the presence of high concentrations of materials in the soap additive slurries commonly used to enhance the appeal of soap.
To avoid such problems, it was suggested that the high concentrations of the dye for the highly-colored bars be added to the slurry mixing tank.
The disadvantage in such a coloring method is that a separate slurry tank has to be used for each color of soap; whereas in the method for dyeing pastel soaps, one slurry tank could be used to make a master slurry to be fed to a number of almagamators. So, the change from the practice of introducing dye in the amalgamator to the practice of introducing dye in the slurry tank would require additional slurry tanks, additional factory space and additional personnel to operate the equipment.
It is, therefore, an object of this invention to provide a more efficient method for introducing in the amalgamator a high concentration of dye to homogeneously color soap pellets and synthetic detergents and combinations thereof.
It is further an object of this invention to provide a superior high-concentration dye system for use in dyeing soaps and synthetic detergents in the amalgamator.